There is a paucity of data regarding the microbial constituents of tobacco products and their impacts on public health. Specifically, there has been no comparative characterization performed on the bacterial microbiota associated with mentholated versus non-mentholated cigarette tobacco, and how these differences could potentially impact the health of menthol versus non-menthol cigarette users.
To address this knowledge gap, we conducted time series experiments with five different commercially-available brands of cigarettes (menthol and non-menthol varieties) placed under three different conditions of temperature and relative humidity. On days 0, 5, 9 and 14, subsamples of each product were subject to DNA extraction using enzymatic and physical lysis. Following purification, the DNA was amplified in PCR assays of the V3-V4 hypervariable regions of the 16S rRNA gene, and the resulting 16S PCR amplicons were sequenced on the Illumina MiSeq platform. Sequences were then analyzed using the QIIME analysis software, as well as with the MetagenomeSeq package implemented in R.
2,046 different bacterial OTUs were identified from a total of 388,6999 sequences. 27 different bacterial phyla were identified, with dominant phyla (>5.0%) being Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. Many of the microorganisms detected were OTUs uncharacterized at the genus level ; however, mentholated tobacco seems to select for hardy bacteria that are able to withstand extreme environmental conditions (elevated pH, wastewater/sediment environments, industrial processes). Mentholation also seems to reduce rhizospheric bacteria.
These data provide preliminary evidence that the mentholation process used in the production of commercially-available cigarettes can impact bacterial communities in these products, possibly selecting for microorganisms that are resistant to harsher environmental conditions. However, because 1) many of the tobacco-associated bacteria detected here are poorly characterized; and 2) the overall public health implications of these findings are unclear, additional studies are warranted.